1. Field of Invention
The present invention relates to apparatus for controlling the depth of marine cables.
2. Description of Prior Art
U.S. Pat. No. 3,931,608, of which applicant is inventor, was an apparatus for controlling the depth of a marine cable, such as a geophysical exploration cable during marine seismic exploration. The apparatus of this patent departed from other depth controllers, such as in U.S. Pat. Nos. 3,375,800 and 3,434,446 of which applicant is also an inventor, by moving the housing which contained the depth controlling mechanism from a position enclosing the seismic cable to a position spaced from the cable by a support shank so as to reduce noise induced into the cable and improve performance.
The depth controller apparatus of U.S. Pat. No. 3,931,608 included a prow member adapted to deflect marine growth and debris away from the depth controlling diving planes as the depth controller was towed with the seismic cable through the water. However, often seismic exploration is performed in areas where buoys and other floating objects as well as fishing lines and traps are deployed in the water. These types of objects are often suspended in the water by wire or metal lines or cables. When a seismic exploration passed near these types of objects, the line often contacted the diving control wings or planes of the depth controller, damaging the depth controller.
Attempts have been made, as in U.S. Pat. No. 4,027,616, to protect the depth control vanes of cable depth controllers of one particular design in a cage or mask-like enclosure. However, this type of protection device was mounted, along with the depth control vanes, along the longitudinal axis of the seismic cable and thus did not, so far as is known, permit relative movement of the depth controller with respect to the cable when a line was encountered.